Effect of Glycine and Triton X-100 on secretion and expression of ZZ–EGFP fusion protein

Two-factor and three-level fractional factorial design was employed for evaluation of the effect of Glycine and Triton X-100 on the secretion and expression of ZZ–EGFP fusion proteins. Varying contents of glycine (0%, 1%, 2%) and Triton X-100 (0%, 1%, 2%) were added into shaking flasks, respectively, and supplied with appropriate volume of ampicillin (total 9 combinations; group at concentration zero serving as control) to promote more ZZ–EGFP diffuse into liquid culture medium. Fluorescent intensity in the culture supernatant was detected. A standard curve could be generated on the basis of fluorescent intensity and protein concentration. The expression level of ZZ–EGFP fusion proteins was estimated by checking the protein standard curve concentration fluorescene intensity. Results show that when the culture medium contains 2% Glycine and 1% Triton X-100, the expression level of ZZ–EGFP was able to be greatly increased. Further experiments revealed that absorbance value (A₆₀₀) in the experiment group, whose culture medium contains 2% Glycine and 2% Triton X-100, is significantly lower than other groups in the present experiment. These results indicate that the culture medium containing appropriate quantity of Glycine and Triton X-100 is favourable to the secretion and expression level of ZZ–EGFP in gene-engineering bacteria Escherichia coli HB101.     

光敏化作用对曲霉孢子失活的影响

通过曲霉孢子与光敏剂的孵育、光照、平板菌落计数、计算孢子失活率实验,结合荧光显微镜观察孢子产生的荧光,探讨光敏化作用对曲霉孢子的影响。结果表明,孵育时间对孢子失活率影响不大,光敏剂浓度>100μg/mL且光照时间为60min时孢子失活率能达到80%以上,并且黑曲霉孢子对光敏化作用比黄曲霉孢子更敏感,无光照时2种曲霉孢子对此方法都不敏感。因此,光敏化作用对2种曲霉孢子有明显的抑制作用。     

猪软革断裂伸长率的部位差异

从猪软革断裂伸长率方面研究了取样部位对其物性的影响.将整张皮革各部位有关数据的平均值与按国家标准取样所得值进行比较,结果是标准部位在断裂伸长率等方面代表整张猪软革的平均值并不合适.     

基于知识工程的模具设计

模具设计需大量的知识与经验,这限制了人们缩短模具开发周期的努力.为了改变这种状况,利用知识工程技术建立模具设计框架进行辅助设计,减少了人们对设计经验的过度依赖,缩短了模具开发周期.     

Worldwide aflatoxin contamination of agricultural products and foods: From occurrence to control

Aflatoxins represent a global public health and economic concern as they are responsible for significant adverse health and economic issues affecting consumers and farmers worldwide. Produced by fungal species from the Aspergillus genus, aflatoxins are a toxic, mutagenic, and carcinogenic group of fungal metabolites that routinely contaminate food and agricultural products. Climate and diet are essential factors in the aflatoxin contamination of food and subsequent human exposure process. Countri es with warmer climates and staple foods that are aflatoxin-susceptible shoulder a substantial portion of the global aflatoxins burden. Enactment of regulations, prevention of pre- and postharvest contamination, decontamination, and detoxification have been used to prevent human dietary exposure to aflatoxin. Exploiting their chemical and structural properties, means are devised to detect and quantify aflatoxin presence in foods. Herein, recent developments in several important aspects impacting aflatoxin contamination of the food supply, including: fungal producers of the toxin, occurrence in food, worldwide regulations, detection methods, preventive strategies, and removal and degradation methods were reviewed and presented. In conclusion, aflatoxin continues to be a major food safety problem, especially in developing countries where regulatory limits do not exist or are not adequately enforced. Finally, knowledge gaps and current challenges in each discussed aspect were identified, and new solutions were proposed.     

聚乙烯醇增强纤维用于口罩贴肤层过滤纸的研究

研究了聚乙烯醇纤维(PVAF)不同添加量对口罩亲肤层过滤纸性能的影响。实验结果表明:纸张的干强度随PVAF添加量的增加而提高;纸张的湿强度在PVAF添加量小于3%时没有改善,当PVAF添加量在3%~7%时,纸张的湿强度明显提高,当PVAF添加量大于7%,纸张湿强度的增加趋势变缓。纸张透气度随PVAF添加量的增加而降低,添加量大于3%以后,透气度下降趋势变缓。添加PVAF对纸张的吸水速度有所影响,但下降幅度较小。     

蛋清蛋白对豌豆淀粉凝胶化及凝胶特性的影响

为探究蛋清蛋白对豌豆淀粉凝胶化及凝胶特性的影响。分别以0%、3%、6%、9%和12%的蛋清蛋白替代豌豆淀粉,研究蛋清蛋白对豌豆淀粉糊化特性、热特性、静态流变、动态流变、凝胶质构及水分子状态的影响。结果表明：蛋清蛋白以浓度依赖的方式影响豌豆淀粉的糊化特性,峰值黏度、谷值黏度、崩解值、最终黏度、回生值均随蛋清蛋白添加量增加而降低,而糊化温度则升高。蛋清蛋白对豌豆淀粉凝胶化温度影响不显著,但降低了淀粉的凝胶化焓值。添加不同量蛋清蛋白的豌豆淀粉糊均表现为假塑性流体特征,Herchel-Bulkley模型能够很好地拟合其静态流变行为,稠度指数和屈服应力均随蛋清蛋白添加量增加而降低。添加蛋清蛋白降低了豌豆淀粉糊体系的黏弹性及凝胶的硬度、强度和可塑性。蛋清蛋白对豌豆淀粉凝胶中自由水含量影响不显著,但使结合水含量增加而不可流动束缚水含量降低。     

基于综合指标TOPSIS法的电网节点脆弱性评估

提出综合改进指标和逼近理想排序法(Technique for Order preference by Similarity to Ideal Solution,TOPSIS)的方法,实现对节点脆弱度的评估。从结构和状态两个角度,分析当前节点脆弱性评估中的不足,定义电气耦合距离重新度量节点间距,从负载率、负载均衡度和失负荷等角度定义故障影响因子,用二者改进度、凝聚度和紧密度等指标,构建综合脆弱性指标体系。用指标大小对传统信息熵进行修正,解决其中的对称性问题,得到客观权重,根据指标作用设置主观权重,将二者结合得到综合权重。最后,提出多属性决策的思想,运用灰色关联度改进的TOPSIS法,实现节点脆弱度的评估。以IEEE14节点系统为例验证了所提方法的有效性和可行性。